1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device.
In this specification, a semiconductor device refers to all devices that can operate by utilizing semiconductor characteristics. Thus, electro-optical devices, semiconductor circuits, and electronic devices are all included in the category of the semiconductor device.
2. Description of the Related Art
A technique for forming a transistor by using a semiconductor film formed over a substrate having an insulating surface has attracted attention. The transistor is applied to a wide range of electronic devices such as an integrated circuit (IC) and an image display device (display device). A silicon-based semiconductor film is widely known as a semiconductor film applicable to the transistor. As another film, an oxide semiconductor film has attracted attention.
As for a transistor including an oxide semiconductor film, better electric characteristics have been required for application to semiconductor devices with higher performance. A technique by which a transistor including an oxide semiconductor film, which can operate at high speed, is obtained owing to reduction in parasitic capacitance by self-aligned formation of low-resistance source and drain regions by an aluminum reaction method has been reported (see Non-Patent Document 1).